1. Field of the Invention
The invention relates to a self-propelled road milling machine for milling road surfaces, in particular large-scale milling machines, and a method for milling road surfaces.
2. Description of the Prior Art
Road milling machines having a milling width of approximately 1500 mm and more are referred to as large-scale milling machines, for example. Such road milling machines have a large weight and are thus normally supported by a chassis comprising crawler-type traveling gears. The milling roller is supported at the machine frame between the traveling gears of the front axle and the rear axle in spaced relationship to the axles. Large-scale milling machines comprise a height adjustable chassis including front and rear traveling gears which define the front axle and the rear axle, respectively. The machine frame is supported by the chassis, wherein between the axles of the front and rear traveling gears a milling roller housing is arranged at the machine frame, which comprises a single roller mill rotatably supported in the milling roller housing. The milling roller housing has coupled thereto, via a belt shoe, a conveyor belt means for removing the milling product milled-off and ejected by the milling roller in forward direction, as seen in the direction of travel.
Such a large-scale milling machine is known from EP 2 011 921 A, for example.
A front end of the milling roller housing is nearly flush with an outer side of the machine frame, the so-called zero side, to allow milling to be performed as near as possible to edges or obstacles. The milling roller housing is not adjustable in height relative to the machine frame such that the overall machine weight can be transmitted to the milling roller to produce high cutting forces and thus a large milling depth.
So far large-scale milling machines have been used mainly for milling large surfaces only, inter alia, because of their limited maneuverability, wherein, depending on the course of the road, it has been possible to perform milling work in curves of the road having a large curve radius.
In particular during milling work performed towards the inside relative to the zero side large-scale milling machines are problematic in that it has not been possible for the machine operator to follow a curve with a narrow curve radius. A solution to this problem is described in EP 2 011 921, which allows for a visual check when steering a large-scale milling machine, whereby the maneuverability of a large-scale milling machine could be improved.
In the case of roads with right-hand traffic, the zero side of a road milling machine is preferably provided on the right-hand side of the machine, as seen in the direction of travel. In the case of roads with left-hand traffic, the zero side is preferably provided on the left-hand side (as seen in the direction of travel). It is understood that a large-scale milling machine can be turned around when there is enough room for a turning maneuver and thus a large-scale milling machine having the zero side on the right-hand side, as seen in the direction of travel, can also be used on roads with left-hand traffic. This is disadvantageous in that the road milling machine having its zero side on the right-hand side, as seen in the direction of travel, has to travel opposite to the moving traffic when a road cannot be completely closed when roadwork is performed. Such a situation is encountered, for example, when on a highway the left-hand traffic lane is to be milled flush with the left-hand side of the road. This is disadvantageous in that the trucks receiving the milled-off product in front of the road milling machine must also travel opposite to the traffic flow to the front side of the road milling machine and then travel away from there. Further, when narrow roads are concerned it is often desirable to be able to optionally mill the road on the left-hand or the right-hand side without the need to turn the large-scale milling machine.
For example, in DE 83 15 139 U it is provided that in a road milling machine supported by a wheel-type traveling gear a single hydraulically operated milling roller is displaced transversely to the direction of travel by a small stroke along sliding guides. The machine concerned is not a large-scale milling machine which can produce large cutting forces since the milling roller is supported such that it is pivotable about a horizontal axis and rests on the ground merely due to its dead weight. The milling roller can thus be raised and lowered relative to the machine frame and further can be pivoted about an axis extending in the direction of travel to adapt to the inclination of the road. The capability of being transversely displaced is to allow for an accurate control of the milling track. It is understood that due to this rocker support of the milling roller no large cutting forces can be exerted and such a milling machine is suitable only for milling surfaces where no large milling depths are required.